1. Field of the Invention
The present invention relates to a method of manufacturing a BGA (Ball Grid Array) semiconductor package and, more particularly, to a method of manufacturing a BGA using a flexible circuit board.
2. Discussion of Related Art
As a rule, `semiconductor package` refers to an electronic device provided with I/O terminals for the transmission of signals to a main board by using, for example, lead frame, PCB (Printed Circuit Board), flexible circuit board, or the like and encapsulated with an encapsulant in order to protect a semiconductor chip, e.g., single device and/or integrated circuitry having all sorts of electronic circuits and/or wirings against unfavorable environments such as dusts, moisture, external shock, or electrical or mechanical load and also to achieve an optimization of the semiconductor chip's performance.
Such semiconductor packages are in the rapid development for high integration, miniaturization and high performance with the trends of producing electronic devices of high performance and miniaturization and, therefore, surface built-in semiconductor packages such as SOJ (Small Outline J-leaded Package) or QFP (Qquad Flat Package) are widely used for the resin encapsulated semiconductor packages using lead frames. Recently, the use of printed circuit boards or flexible circuit boards in a ball grid array semiconductor package can maximize the number of input/output terminals and increase the built-in density in a main board, contributing to the miniaturization and high performance of semiconductor packages.
Generally speaking, such a ball grid array semiconductor package has one or more semiconductor chips mounted on a PCB, and an array of solder balls disposed in the opposite position to the PCB with the semiconductor chip attached thereon and providing an electrical connection with respect to the conductive material such as main board. Ball grid array semiconductors having such a structure are widely used in a multi-pin device above 200 pins, VLSI (Very Large-Scale Integrated) circuits, micro processors, and the like.
The ball grid array semiconductor package, however, has very high heat resistance due to the PCB's thickness of at least a several hundreds of microns, thus deteriorated by a heat generated during the operation of the mounted semiconductor chip, unsatisfactory in the requirements for light-weighted and thin devices, and needed to form a solder mask to cover the whole PCB and its circuit patterns for the purpose of insulating the circuit patterns exposed out of the encapsulant section. For a multi-structured PCB, it is necessary to form via holes for electrical connections between upper and lower circuit patterns, increasing the complexity of process and the production cost.
The example of FIG. 3 is substantially similar to the structure of a semiconductor package using a conventional flexible circuit board. With reference to FIG. 3, the semiconductor package comprises a semiconductor chip 20 having laminated electronic circuits and/or wirings and plural I/O pads 10a formed on the surface; a flexible circuit board 40' having a circuit pattern 42 which is formed on a flexible resin film 41 with an adhesive coating 30 coated on the lower surface a semiconductor chip 20 and includes a plurality of conductive traces having fingers 43 and conductive ball lands 44 as I/O terminals, the semiconductor chip 20 being mounted on the center of the flexible circuit board 40' with adhesive coating 30; conductive wires 50 for electrically connecting the I/O pads 10a of the semiconductor chip 20 to the bond fingers 43 of the flexible circuit board 40'; a resin encapsulant section 60 for protecting semiconductor chip 20 and conductive wires 50 against external environments; and conductive balls 70 adhesively fused to the conductive ball lands 44 electrically connected to the circuit pattern 42 of the flexible circuit board 40', and functioning as I/O terminals to a main board.
However, in a method of the ball grid array semiconductor package using the flexible circuit board according to prior art, the metal carrier frame with the flexible circuit board attached thereon must be cut by means of punch or cutter in the step of singulation to separate a plurality of ball grid array semiconductor packages in the piece formed on a single strip for the process efficiency, thereby producing deflection or damages on the minute conductive traces positioned in the outer part of circuit patterns formed on the flexible circuit board, with consequence of short-circuits.
It is therefore an increasing trend to manufacture a ball grid array semiconductor package using a flexible circuit board wherein circuit patterns are formed on a very thin, flexible resin film, instead of using a PCB board that has a relatively large thickness.